show column group header when dragging
show column group header when dragging

phoebusliang/ember-table,hedgeserv/ember-table,phoebusliang/ember-table,nomadop/ember-table,Cuiyansong/ember-table,Gaurav0/ember-table,Cuiyansong/ember-table,hedgeserv/ember-table,nomadop/ember-table,Gaurav0/ember-table